|Publication number||US7651739 B2|
|Application number||US 11/450,169|
|Publication date||Jan 26, 2010|
|Priority date||Oct 10, 2005|
|Also published as||US20070082138|
|Publication number||11450169, 450169, US 7651739 B2, US 7651739B2, US-B2-7651739, US7651739 B2, US7651739B2|
|Inventors||In Kyu You, Seung Youl Kang, Seong Deok Ahn, Gi Heon Kim, Ji Young Oh, Chul Am KIM, Kyu Ha Baek, Kyung Soo Suh|
|Original Assignee||Electronics And Telecommunications Research Institute|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (1), Classifications (21), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims priority to and the benefit of Korean Patent Application No. 2005-94823, filed on Oct. 10, 2005, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a fiber reinforced plastic (FRP) substrate applied to a flexible electronic device, and more particularly, to a surface treatment method of an FRP substrate which can improve surface flatness and prevent failures due to misalignment in a process of fabricating a device.
2. Discussion of Related Art
Flexible electronic devices have been the focus of considerable attention and world-wide studied since the mid-1990s. Flexible electronic devices are applied in various fields, such as in attachable displays, advertising displays, large portable displays, and the like. The leading applications are electronic paper and organic light emitting devices (OLEDs), and a field of applications using organic thin film transistors is on the forefront of development.
As an interest in flexible electronic devices increases, research into some materials as flexible substrate is progressing. Exemplary materials used for a flexible substrate are polyether sulfone (PES), poly ethylene tertraphthalate (PET), poly ethylene naphthalate (PEN), poly imide (PI), poly carbonate (PC), and the like. These materials, as shown in the following Table 1, have a relatively high glass transition temperature (Tg) in the range of about 150-220° C., and a coefficient of thermal expansion (CTE) of about 15-70 ppm/° C. (@ 55-85° C.).
CTE(−55–85° C.)/ppm/° C.
*GPa: Giga Pascal
However, in spite of these properties, there are many difficulties in using these materials as a substrate of a flexible electric device, because a substrate swelling, expansion, or shrinking while undergoing a photolithography process, a thermal process, a chemical process, and the like, in the manufacture of a practical electronic device.
Accordingly, both PC and PES substrates have a problem of expansion by 15 μm or more per 5 cm. This problem can become quite serious when the substrates are actually used to form electronic devices. In order to form an organic flexible active-matrix OLED and electronic paper, while there is a slight variation depending on the complexity of the device to be formed, photolithography processes should be performed at least six times. However, when such misalignment happens, a device cannot be integrated, and in the case of an organic luminescent emitting display having a 5 cm panel, a part of the panel may not operate owing to misalignment.
Therefore, in order to easily form a fine pattern of a highly integrated device, a plastic substrate that does not expand, shrink or deform significantly should be used. However, plastic substrates currently being used do undergo deformation such as expansion and shrinking in a process of fabricating a device, and have very low surface smoothness, therefore making them difficult to employ in device manufacture.
The present invention is directed to providing a surface treatment method of a fiber reinforced plastic (FRP) substrate for fabricating a device.
The present invention is also directed to providing a surface treatment method of an FRP substrate for improving surface smoothness of the FRP substrate and preventing failures due to misalignment in a photolithography process.
According to one aspect of the invention, there is provided a surface treatment method of an FRP substrate, comprising: cleaning the FRP substrate; removing residue from the surface of the FRP substrate; coating the FRP substrate with an organic insulating solution and planarizing the surface thereof; and baking the organic insulating solution.
The step of cleaning the FRP substrate may comprise: cleaning the FRP substrate with a mixed solution of neutral detergent and de-ionized water; cleaning the FRP substrate with de-ionized water and removing organic substances and particles sticking to its surface; cleaning the FRP substrate with a mixed solution of de-ionized water and IPA and removing partially remaining organic substances and inorganic substances; dipping the FRP substrate in IPA and removing partially remaining inorganic substances; and drying the FRP substrate.
The step of planarizing the substrate may comprise dipping the FRP substrate in an organic insulating solution and lifting it out of the organic insulating solution at constant speed.
The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
An FRP substrate has the advantages of being less deformed, i.e., less expanded or shrinked, and being flexible. However, it is difficult to apply it to the fabrication of a practical device owing to low surface smoothness. The invention, by enhancing surface smoothness through surface treatment, makes the FRP substrate applicable to the fabrication of flexible displays, flexible electronic devices, fine flexible organic electronic devices, and flexible active OLEDs using the fine flexible organic electronic devices as driving devices.
Hereinafter, exemplary embodiments of the present invention will be described in detail. However, the present invention is not limited to the exemplary embodiments disclosed below, but can be implemented in various modified forms. Therefore, the exemplary embodiments are provided for complete disclosure of the present invention and to fully inform the scope of the present invention to those of ordinary skill in the art.
Cleaning (Step 31)
An FRP substrate is cleaned. The present exemplary embodiment of the invention uses an FRP substrate that is 100 μm thick, and an example of the cleaning step is as follows.
First, the FRP substrate is cleaned for about 5 to 10 minutes with a mixed solution of neutral detergent and de-ionized water in a ratio of 1:5. The cleaned FRP substrate is cleaned for 5 to 10 minutes with de-ionized water in an ultrasonic washer so that organisms or particles, sticking to the surface due to static electricity, are removed. In order to remove partially remaining organic and inorganic substances, the substrate is cleaned for 5 to 10 minutes with a mixed solution of de-ionized water and IPA in equal ratio. Also, the FRP substrate is dipped in IPA for 5 to 10 minutes so as to remove remaining inorganic substances, and then oven-dried for 10 minutes at 100° C.
Removing Residue (Step 32)
The substrate is heat-treated in an oven for 24 to 48 hours in a vacuum and at a temperature of 100 to 180° C., and preferably 150° C. Volatile residue materials are removed by this heat treatment. When materials such as water, any sort of organisms, gas compounds and the like remain on the surface of the FRP substrate, they may affect the properties of a device.
Coating and Flatness (Step 33)
A surface of the FRP substrate is planarized by coating the heat-treated FRP substrate with an organic insulating solution. Here, it is important that the organic insulating materials are evenly coated on the surface of the FRP substrate. In an exemplary embodiment of the invention, the FRP substrate is dipped for over 30 minutes in the organic insulating solution and then lifted out with a dipper (dragger) so that the organic insulating solution may be evenly coated on the surface of the FRP substrate. Here, when the FRP substrate is lifted up at a constant speed, surface smoothness may deteriorate, for example, patterns may be formed on the surface. This is why the substrate is preferably lifted up at a slow and constant speed, for example, at a constant speed of 0.1-1 mm/s. Alternatively, any other coating method that maintains surface smoothness may be applied in lieu of the dipping method. As the organic insulating solution, acryl-based JSS362 or JSS361 available from JSR Company can be used. Or, a polymer solution containing any of polyester, polycarbonate, polyvinylbuterate, polyethylene, polyamide, polysulphone, polyvinylacetylene, polyacrylate, and polyvinylalcohol, for example, may also be used as the organic insulating solution.
Baking (Step 34)
As described above, the FRP substrate coated with the organic insulating solution is baked by heat-treating in an oven for 30 minutes to 1 hour, in a vacuum and at a temperature of 100 to 180° C., and preferably 150° C.
For example, in the case of fabricating a display emitting device, alignment should be made less than ¼ of the design rule in order for all pixels in a panel to operate normally. While there is some difference depending a cell size and structure, 2 inch QVGA panel integration is possible within 1.25 μm or less assuming a design rule of 5 μm.
As mentioned above, the invention uses an FRP substrate that deforms less than a conventional flexible substrate material, and improves its surface smoothness in order to apply the FRP substrate to device fabrication. In the invention, the surface of the FRP substrate is smoothed by coating with an organic insulating solution. An FRP substrate whose surface treated according to the invention is flexible, less thermally deformed, and has superior surface smoothness, so that failures due to misalignment in a photolithography process may be prevented.
An FRP substrate whose surface has been treated according to the invention may be applied to the fabrication of flexible displays, flexible electronic devices, fine flexible organic electronic devices, and flexible active OLEDs using flexible organic devices as driving ICs.
Although a few embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|WO2016018329A1 *||Jul 31, 2014||Feb 4, 2016||Hewlett-Packard Development Company, L.P.||Opaque-plastic film on a fiber surface|
|U.S. Classification||427/384, 427/430.1, 427/331, 427/299, 134/26, 427/372.2, 427/307|
|International Classification||B05D1/18, B08B3/10, B05D3/02, B05D3/00|
|Cooperative Classification||Y02E10/549, H05K1/0366, C08J7/047, H01L51/0097, H05K2203/0759, H05K1/0393, H05K3/386|
|European Classification||C08J7/04L, H05K3/38D, H01L51/00S2|
|Jun 8, 2006||AS||Assignment|
Owner name: ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTIT
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:YOU, IN KYU;KANG, SEUNG YOUL;AHN, SEONG DEOK;AND OTHERS;REEL/FRAME:017967/0942
Effective date: 20060503
|Mar 15, 2013||FPAY||Fee payment|
Year of fee payment: 4